double to json bug

```
Delphi7 
Windows xp

procedure TForm1.Button1Click(Sender: TObject);
var
  jo: ISuperObject;
begin
  jo := so('{a:1}');
  jo.D['a']:=1.0;
  ShowMessage(jo.AsJSon(False,false));
end;

output:
{"a":1.}

  '1.' is not a valid json number，it should be '1.0'

```

Original issue reported on code.google.com by `lizhen...@gmail.com` on 21 Feb 2011 at 3:49
